A PWM static VAr compensator based on phase-shift-controlled multiple-bridge superposition harmonic elimination technique

In this paper, a four-bridge PWM static VAr compensator (FB-PSVC) based on an improved version of the PWM controller is presented in this paper, and a novel phase-shift-controlled multiple-bridge superposition harmonic elimination technique is also proposed. Theoretical analysis shows that the harmonic pairs of [(2k+1)f_s±f] and [(4k+2)f_s±f] generated in each bridge are effectively eliminated through appropriate phase shift control. To satisfy the same total harmonic distortion (THD) requirement (usually under 5%), this new compensator can work at 200 Hz, which is much lower than the previously reported 1.9 kHz of a single-bridge PWM static VAr compensator (SB-PSVC). The efficiency is increased and reliability enhanced. The fairly low switching frequency and multiple bridge structure facilitate its use in high-power VAr compensators since GTOs can be employed as power switch. Theoretical analysis was verified through simulations and experimental results